Novel Source of Resistance against Root Necrosis and Plant Wilting Disease Caused by Phytophthora nicotianae in Capsicum annuum

Phytophthora nicotianae the causal agent of root necrosis in pepper was isolated and identified for the first time in Tunisia in 1995. It causes plant wilting and might induce considerable damage especially in infested soils grown with pepper varieties lacking genetic resistance. This disease was observed in green houses as well as in open fields. The present study aimed to identify sources of resistance against P. nicotianae in a collection of pepper accessions from the WorldVeg (The World Vegetable Center, previously named AVRDC for Asian Vegetable Research and Development Center) gene bank. These WorldVeg accessions include 28 chili and 12 sweet peppers together with 8 chili and one sweet local cultivars. Seedling reaction to the pathogen was determined one month after inoculation by the zoospores of a highly aggressive isolate deposited at the seedling crown. Results showed that 12 accessions (11 chili and 1 sweet peppers) displayed good resistance to this oomycete. However, fruit quality and productivity of these resistant accessions need to be verified. It is of importance to carry out an analysis on genetic control of such resistance by performing crosses between susceptible and resistant ones, besides studying the suitable use of the unveiled resistance according to the pathogenicity and virulence of the pathogen strains. Therefore, appropriate resistance sources can be used as genitors in a breeding program.